1-benzyloxymethyl-1H-benzimidazole → (1-benzyloxymethyl-1H-benzimidazol-2-yl)-(3-bromothiophen-2-yl)methanone

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 1-benzyloxymethyl-1H-benzimidazole (648 mg, 2.72 mmol, Example 1B) in tetrahydrofuran (15 mL) at −78° C. under nitrogen is added n-butyllithium (1.30 mL of a 2.5 M solution in hexanes, 3.25 mmol) over 5 minutes and the resulting yellow solution is stirred at −78° C. After 25 minutes, a solution of 3-bromo-thiophene-2-carboxylic acid methoxy-methyl-amide (680 mg, 2.72 mmol, Example 1A) in tetrahydrofuran (10 mL) is added over 15 minutes and the reaction stirred at −78° C. After 1 hour the reaction is warmed to ambient temperature and stirred for an additional 2 hours. The reaction is quenched with saturated ammonium chloride and the mixture extracted with ethyl acetate. The organic layer is washed with water and brine successively, dried over magnesium sulfate, and concentrated under reduced pressure to a yellow oil. The crude material is chromatographed on silica, eluting with 40% ethyl acetate/heptane, to give the product. Trituration with ether/heptane affords (1-benzyloxymethyl-1H-benzimidazol-2-yl)-(3-bromothiophen-2-yl)methanone as an off-white powder; TLC Rƒ0.52 (silica, 1:1 ethyl acetate/heptane); LC/MS: (M+H 427.0, RT=3.84 minutes); 1H NMR[(CD3)2SO), 300 MHz]: δ 8.18 (d, 1H, 5.2 Hz), 7.90-7.82 (m, 2H), 7.55-7.50 (m, 1H), 7.45-7.38 (m, 2H), 7.25-7.17 (m, 5H), 6.13 (s, 2H), 4.58 (s, 2H).

Provenance & Evidence